MATERIALS -- POWGEN open for business . . .
The Spallation Neutron Source's Powder Diffractometer POWGEN has launched a rapid access sample mail-in system for users who use the flexible general-purpose instrument for a wide range of structural studies of novel materials. The instrument will be made available to rapid access users for a few days each cycle, offering data collection for two temperatures between 12 degrees Kelvin and 300 degrees Kelvin per sample. Users with a new material to test will not have wait six months for beam time. If response is good, the instrument could run tests on as many as 24 mail-in samples over two days. The instrument scientists would send back the data to the users. POWGEN specializes in magnetic materials such as high-Technitium superconductors and metal insulator phase transitions as well as nonmagnetic materials, polycrystalline materials for pharmaceutical compounds, metals and semi-conductors and new battery materials. [Written by Agatha Bardoel; media contact: Ron Walli, (865) 576-0226; wallira@ornl.gov]
CHEMISTRY -- Unraveling methane's structure . . .
Considering how ubiquitous it is on earth, methane (natural gas) at the molecular level is a scientific unknown. To understand it and to manage it both as energy and as an environmental hazard, scientists need to know more about its molecular structure. A neutron diffraction study at the Spallation Neutrons and Pressure Diffractometer at Oak Ridge National Laboratory has successfully mapped the structure of methane and water cages, known as clathrates, under more than half a million pounds of pressure per square inch. The researchers came up with a new potential ─ a new calculation of the repulsion force that exists between methane molecules in these cages ─ that indicated there were five methane molecule "guests" inside the enlarged polyhedral structures that emerged under the high-pressure conditions. [Written by Agatha Bardoel; media contact: Ron Walli, (865) 576-0226; wallira@ornl.gov]
BIOLOGY -- Model tells the story . . .
Casein micelles in milk, stabilized by molecules of κ-casein, are the building blocks of dairy products such as yogurt and cheese and the vehicle for delivering calcium phosphate to newborns. Several models for the internal structure of these have been proposed. Using contrast variation small-angle neutron scattering at the General Purpose SANS instrument at Oak Ridge National Laboratory's High Flux Isotope Reactor, researchers have confirmed that one model prevails: Casein micelles are composed of a protein matrix in which the calcium phosphate nanoclusters (about 300 per casein micelle) are dispersed. The protein matrix has local density fluctuations that may be ascribed to the hydrophobic interactions of these proteins. A new method was developed and used to calculate the scattering spectra of composite particles. [Written by Agatha Bardoel; media contact: Ron Walli, (865) 576-0226; wallira@ornl.gov]
CHEMISTRY -- Workshop helps student earn publication . . .
An Oregon State University graduate student has successfully turned her participation in a two-day POWGEN Neutron Diffraction workshop at Oak Ridge National Laboratory's Spallation Neutron Source into a published paper in the Journal of Solid State Chemistry. Participants at the workshop in September were invited to bring their own samples for analysis on the time of flight diffractometer. They received training on the instrument and then were taught how to collect and analyze the data. Rosa Grajczyk, a second-year PhD student in chemistry working on structural properties of new materials, brought a solid solution of indium-gallium-magnesium-oxide to the workshop as part of her thesis work. "The amount of detail that went into the workshop was incredible," Grajczyk said, "and I was facilitated by the helpfulness of everyone at the facility." Her paper on the lattice structure of the new material was accepted in the Journal of Solid State Chemistry. [Written by Agatha Bardoel; media contact: Ron Walli, (865) 576-0226; wallira@ornl.gov]
PHYSICS -- Searching for 'supersolidity' . . .
Theoretical physicists have long predicted the existence of a quantum state of matter they call "supersolidity," in which solid helium-4 loses its viscosity and flows like a liquid. Researchers are using the Spallation Neutron Source in a series of studies to pin down whether this paradoxical new state of matter can be demonstrated. The experiments involve growing crystals of solid helium inside a one-of-a-kind sample cell at almost absolute zero temperature and crushing pressure. The scientists have seen tantalizing signs of what they are seeking, but not proof, as yet. The experiments are continuing. [Written by Deborah Counce; media contact: Ron Walli, (865) 576-0226; wallira@ornl.gov]